Merge pull request #1451 from diegosarmentero/master

updates in travis and readme
Update .travis.yml

Add xvfb (X Virtual Framebuffer) virtual screen support for future testing.
According to official Docs at:
http://about.travis-ci.org/docs/user/gui-and-headless-browsers/#Using-xvfb-to-Run-Tests-That-Require-GUI-(e.g.-a-Web-browser)
Merge pull request #1452 from juancarlospaco/patch-1

Update .travis.yml
Update .travis.yml

Add sip to pip
Merge pull request #1453 from juancarlospaco/patch-2

Update .travis.yml
Update .travis.yml
Merge pull request #1454 from juancarlospaco/patch-3

Update .travis.yml
Update .travis.yml

Wildcards * are not allowed on apt-get commands
Merge pull request #1455 from juancarlospaco/patch-4

Update .travis.yml
Fixes Issue #1416
Merge remote-tracking branch 'upstream/master'